1. Field of the Invention
The present invention relates to a turbine rotor.
2. Description of Related Art
Energy conservation and environmental conservation, and in particular reduction in CO2 has begun to attract growing interest, and it is desired in the field of a steam turbine power generation plant to increase the capacity and enhance the thermal efficiency. Enhancement in thermal efficiency is achieved by increasing the temperature and pressure of steam, and further increase in temperature is planed in future. The first stage blade of a high pressure turbine is the first element to be exposed to steam among rotating elements, and it is necessary to secure durability to high-temperature and high-pressure steam, and in particular to secure strength reliability, among others.
In a conventional material including iron as a main component, if the main steam temperature exceeds 650° C., the high-temperature strength, in particular creep strength, abruptly reduces. The countermeasures against high-temperature steam have been taken by cooling of a rotating body and the like so far. JP-A-2004-239262 and JP-A-2002-508044 each describe a method of cooling a rotor by providing a cooling hole extending from the inside of a shaft of a rotor shaft to an intermediate portion between discs, and by passing a cooling medium in the cooling hole. JP-A-7-145707 and JP-A-7-42508 each describe a cooling method in which a cooling hole is provided in a bottom of a rotor disc. JP-A-2004-169652 describes production of a rotor from an Ni-base super alloy with high heat resistance.